Two striking head-tail galaxies in the galaxy cluster IIZW108: insights into transition to turbulence, magnetic fields and particle re-acceleration

TL;DR

This study uses multi-wavelength observations of two bent tail galaxies in a low-mass galaxy cluster to investigate magnetic fields, particle re-acceleration, and jet dynamics, revealing evidence of ongoing AGN activity and turbulence-induced electron re-acceleration.

Contribution

It provides new insights into the transition to turbulence, magnetic field alignment, and particle re-acceleration mechanisms in galaxy jets within a low-mass cluster environment.

Findings

Spectral index steepening and increased polarization along jets.

Evidence of two AGN outbursts in one galaxy.

Pure electron cooling cannot explain jet lengths.

Abstract

We present deep JVLA observations at 1.4 GHz and 2.7 GHz (full polarization), as well as optical OmegaWINGS/WINGS and X-ray observations of two extended radio galaxies in the IIZW108 galaxy cluster at z = 0.04889. They show a bent tail morphology in agreement with a radio lobed galaxy falling into the cluster potential. Both galaxies are found to possess properties comparable with {narrow-angle} tail galaxies in the literature even though they are part of a low mass cluster. We find a spectral index steepening and an increase in fractional polarization through the galaxy jets and an ordered magnetic field component mostly aligned with the jet direction. This is likely caused by either shear due to the velocity difference of the intracluster medium and the jet fluid and/or magnetic draping of the intracluster medium across the galaxy jets. We find clear evidence that one source is showing two active galactic nuclei (AGN) outbursts from which we expect the AGN has never turned off completely. We show that pure standard electron cooling cannot explain the jet length. We demonstrate therefore that these galaxies can be used as a laboratory to study gentle re-acceleration of relativistic electrons in galaxy jets via transition from laminar to turbulent motion.